System for making continuous sound records



. llg- 7, 1951 J. H. HAMMOND, JR

SYSTEM FOR MAKING CONTINUOUS SOUND RECORDS Filed April :i 194e 2 Sheets-Sheet l INVENTOR JOHN HAYs HAMMoND, JR.

RNEY

VBY

J. H. HAMMOND, JR

SYSTEM FOR MAKING CONTINUOUS SOUND RECORDS Aug. 7, 1951 Filed April :5, 1946 .imi-Juil* Patented Aug. 7, 1951 SYSTEM FOR MAKING CONTINUOUS SOUND RECORDS John Hays Hammond, J r., Gloucester, Mass.

Application anni 3, 1946, serial No. 659,399

4 Claims.

This invention relates to a system for making continuous sound records and more particularly to a system for making a re-entrant magnetic sound record on a continuous circular sound track.

An object of the invention is to provide a system for making a continuous magnetic sound record which is re-entrant with a high degree of accuracy and is adapted to produce a continuous tone without distortion or click at the joined ends of the record.

Another object is to provide a novel and improved system for making a continuous magnetic sound record on a circular disc.

Various other objects and advantages will be apparent as the nature of the invention is more magnetic disc isfrst recorded photographically A on a transparent film. The lm is then cut accurately to contain an integral number of wave lengths and is joined to form a continuous band. The band is then driven synchronously with the magnetic disc, while the sound is picked up photoelectrically from the film and is re-recorded magnetically on the disc. In this system inasmuch as the disc and film are driven at the same speed and the lm contains an integral number of wave lengths, the disc will likewise contain an integral number of wave lengths and the sound tracks will be re-entrant to the degree required, regardless of minor variations in the speed of rotation of the disc or in the frequency of the tone being recorded.

Although the novel features which are believed to be characteristic of this invention are pointed out more particularly in the claims appended hereto, the invention itself will be better understood by referring to the following description taken in connection with the accompanying drawings in which a specific embodiment thereof has been Set forth for purpose of illustration.

In the drawings:

Fig. l is a schematic diagram of a system for recording sound on an endless film; `and Fig. 2 is a schematic diagram of a system for transferring the sound record from the lm to a magnetic disc.

Referring to Fig. 1, a lm II) is shown as mounted on a drum II which is driven by a shaft I2 of a variable speed motor I3, shown as a D. C. motor having a speed control element I4. The iilm IU is secured to the drum by suitable means-shown as a pin I5 or by an adhesive and 2 is cut to a size corresponding generally to the periphery of the drum, although the ends of the iilm may be lapped somewhat as indicated at I6.

The tone to be recorded is derived from a pickup device 23, shown as a microphone, which is connected by lines 2l to a suitable signal amplifier 22, thence by lines 23' to light gate 24 of standard' type which is adapted to vary the intensity of light in accordance with the impressed signal. A light source 25 is positioned to supply light waves through the light gate 24 onto the iilm I0. The light source 25 is preferably actuated by a supersonic frequency supplied from a supersonic generator 26 by lines 2l. The supersonic frequency excitation of the light source prevents distortion of the reproduced sound due to the energizing frequency. AY control switch, shown as a push button 28, is connected to the supersonic generator 2S to control the operation thereof. The operation of the supersonic generator 25 is also controlled by a step-by-step switch 29 which is connected in series to the switch 28y and is actuated by contacts 30. The contacts 39 are positioned to be closed by a lug 3| attached to the drum II at a point corresponding to the beginning and end of the lm I6, as for example the point of the overlapped ends The arrangement is such that the switch 50 is closed each time the lug 3l passes the designated point. The step-by-step switch 29 which may be either mechanical or electrical is arranged to alternately energize and de-energize the supersonic generator 26 upon successive actuations of the contacts 33. Hence when the push button 28 is held closed, the rst actuation of the switch 30 will energize the supersonic generator and cause light rays to be produced by the light source 25 and to be projected through the light gate 24 onto the nlm HI. At the next actuation of the contacts 30 the supersonic generator 26 is cle-energized. Hence the light source is energized only for a single rotation of the drum I I, provided Of course the push button 28 is released before the third actuation of the switch 29 takes place.

An alternator 35 is driven by the shaft I2 of the motor I3 and is adapted to produce a voltage having a frequency corresponding to the frequency of the signal being picked-up by the pickup device 20 or to a sub-multiple thereof. This voltage is supplied by lines 36 to a comparing device sh'own as a cathode ray oscilloscope 3l. A signal from the amplifier 22 is likewise supplied to the oscilloscope 3'I by lines 38. The lines 36 and 38 may be connected to the horizontal and vertical sweep electrodes of the oscilloscope so that a pattern is produced on the oscilloscope screen determined by the relative frequencies of the picked-up signal and the generated voltage.

For example, in order to produce a lm band of 92 complete Waves with a length of about 10 inches the drum ll must be designed to have a circumferential distance of about 20 inches in which 192 Waves could be recorded. In recording a tone having for example 1481.6 cycles per second, the drum would' be required to rotate at 7.72 revolutions per second. The tone generator could be chosen to produce 48 cycles per revolution so that its output Would have 370.4 cycles per second which is a quarter of the signal frequency. The speed of the drive motor is then adjusted so that the oscilloscope pattern corresponds to a 4 to l ratio. Then it Will be certain that inches of the nlm will correspond to 48 cycles of the fundamental tone sought. If, however, the tone frequency varies during the tenth of a second required for recording, the length of the sound track may vary slightly from the nominal value of 10 inches, varying possibly between 9.9 and 10.1 inches.

The rllm thus produced is then developed and cut to contain exactly 96 waves with a high degree of precision and the ends of the film are joined into a band forming a continuous sound track without mechanical discontinuity. Any suitable means may be utilized for joining the ends of the lm. The ends may for example be bias cut so as to eliminate the possibility of a click when the sound is reproduced therefrom. Preferably the ends are joined at a point of maximum sound effect so that any variation at the point of juncture will be masked. The joined film, which is now in the form of a continuous band, may be used as a master record for producing the magnetic records therefrom as shown in the system of Fig. 2.

Referring to Fig. 2, the circular lm band 39 is mounted on a plurality of flexible iingers 40 which are mounted on a spindle 4| and carry Weights 42 which serve to expand the fingers due to centrifugal force when the spindle is rotated, so as to maintain the band 39 in a rigid condition. The spindle 4l is hollow to receive a light source 43 and is secured for rotation on a shaft 44 which is mounted in a bearing block 45, The shaft i4 is driven by suitable means shown as a pulley 46. The pulley, however, may be replaced by a driving motor if desired. The shaft 44 also carries a shoulder 41 to which is secured a magnetic disc 5l! on which the sound is to be recorded. A recording head 5l is positioned to cooperate with the disc 50. This recording head may be of the type disclosed in my copending application Serial No. 643,290, led January 25, 1946, now abandoned, for Magnetic Sound Recording and Pick-Up Device and comprises a magnetic frame having pole pieces 52 and an energizing coil 53.

Light from the source d3, after passing through the nlm 39, is applied to a photoelectric pick-up device indicated at 54 and is of a suitable type to convert variations in light intensity into variations in voltage. The output from the pick-up device 54 is supplied through lines-55 to an amplifier 56 and thence through lines 57 to the coil 53 to produce a magnetic record on the disc 50. inasmuch as the band 39 contains an integral number of waves, it is obvious that the continuous record produced on the disc 50 Will likewise contain an integral number of waves and is adapted for the production of a continuous tone therefrom.

The disc 50 may, for example, be used as a tone disc of an electromagnetic organ of the type described more in detail in my co-pending application Serial No. 646,040, led February 7, 1946, now abandoned, for Electromagnetic Organs.

It will be noted that in the above described system the necessity for accurately synchronizing the magnetic disc with the picked-up signal is avoided as minor variations in frequency are compensated for by the different lengths of the sound track l0 which are joined to form the band 39. The spring fingers 40 are suiciently resilient to accommodate such minor variations in lengths of the band, and to hold the band rigidly as required for reproduction. Manual adjusting means may, however, be provided for adjusting the diameter of the supporting fingers if desired, in which case the centrifugal weights d2 may be omitted.

Although a specific embodiment of the invention has been shown for purposes of illustration, it is to be understood that the invention is capable of various uses and that changes and modications may be made therein as will be readily apparent to a person skilled in the art. The invention is only to be restricted in accordance with the scope of the following claims.

What is claimed is:

l. A signal reproducing system comprising an endless photographic sound record in the form of a circular band, means supporting said band, a magnetic member carrying an endless record track, means driving said band and said magnetic member insynchronism, photo-electric pick-up means connected to respond to the signal recorded on said band, a magnetic recording head ccnnected to respond to said photo-electric pick-up means and positioned to make a continuous magnetic sound record on said track, and means whereby said band supportvmay be adjusted in accordance with variations in length of said band so that a continuous reentrant sound record is provided from which a continuous reentrant magnetic record may be recorded.

2. A signal reproducing system comprising an endless photographic sound record in the form of a circular band, means supporting said band, a magnetic member carrying an endless record track, means driving said band and said magnetic member in synchronism, photo-electric pick-up means connected to respond to the signal recorded on said band, and a magnetic recording head connected to respond to said photoelectric pick-up means and positioned to make a magnetic sound record on said track, said band support comprising a plurality of flexible fingers peripherally disposed about said band for carrying the same and means expanding said fingers for holding said band rigidly in a circular form so that a continuous reentrant sound record is provided from which a continuous reentrant magnetic record may be recorded.

3. A signal reproducing system comprising an endless photographic sound record in the form of a circular band, means supporting said band, a magnetic member carrying an endless record track, means driving said band and said magnetic member in synchronism, photo-electric pick-up means connected to respond to the signal recorded on said band, and a magnetic recording head connected to respond to said photo-electric pick-up means and positioned to make a magnetic sound record on said track, said band support comprising a plurality of flexible ngers peto centrifugal force for expanding the same to hold said band in a rigid circular form so that a continuous reentrant sound record is provided from Which a continuous reentrant magnetic record may be recorded.

4. The method of recording a continuous tone on a re-entrant magnetic sound track which comprises recording said tone on a photographic film, cutting said firm accurately to a length having` an integral number of sound waves, forming said nlm into an endless band, driving said endless band and said magnetic sound track in synchronisin, deriving the recorded signal from said band and recording the derived signal on said magnetic sound track in the form of an endless reentrant recording.

JOHN HAYS HAMMOND, JR.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,555,281 Engl Sept. 29, 1925 1,665,331 Thomson Apr. 10, 1928 1,967,239 Hardy July 24, 1934 2,002,151 Maurer May 21, 1935 2,144,844 Hickmann Jan. 24, 1939 2,209,664 Runge July 30, 1940 2,255,559 Daniel Sept. 9, 1941 FOREIGN PATENTS Number Country Date 12,820 Great Britain 1908 

